Electric time fuse



M y 1935- 7 K. SCHAFFLER-GLGSSL 2,000,617

ELECTRIC TIMEFUSE 7 Filed Feb. 21, 1953 vaqg [rm/anion- I ented May 7,1935 "IED VJVSTAA'TES e 2.000.617 me e TIME FUSE Konra,dSchafller-Gliissl, Vienna, Austriav view, and of which no one can beomitted without impairing the efllcacy of the others. 'I'he inven-' tionrelates more particularly to'electric time fuses of the type comprisinga charge of a re-.

tarding composition tor the purpose of efiecting the timing.

.One of the above mentioned' measures is the provision of a match headwhich, while being capable of easy electric ignition, generates, at thelast stage of the combustion an intense heat withmuch gas generation andwill ensure ignition of the retarding charge even if the latter shouldbe difilcult to ignite. In this respect the intention consists incoating the core of the match head with a layer of. metal powder mixedwith an oxygen carrier. a

Reliable ignition of the retarding charge is further ensured accordingto the invention by enclosing said charge in a cylinder presenting tothe match head a tapered end whereon the heat is concentrated.

A further measure essential for the attainment of the object of theinvention is the use of a retarding charge which will burn at a slowregular rate and which can be stored without degeneration, and in thisrespectthe invention consists in forming the charge from iron powder theparticles of which are coated with a neutral, readily adhering substancesuch as chalk or the like, and mixed in coated condition with an oxygencarrier. The attainment of the object of the invention is furtherconditional onthe provision of an herinetic closure for the differentcharges so that the internal gas .pressure will remain high and withoutfluctuations, in order that the combustion or the retarding charge mayproceed with the desired speed and regularity. In this respect theinvention consists in closing the fuse car.- tridge with a plug of leador other compressible material and sealing said-plug to the cartridgecase and to the leading-in wires by pressing circumierential 5 andsubstantially. continuous grooves into the case and the plug. Experiencehas shown that any leakage of gas from the fuse, and consequentreduction ofthe internal pressure, during the combustion of the delayingcharge, affects the rate at which the latterburns and consequentlyupsets the timing of the fuse.

. closing plug 6' and which supply current for ignit- ApplicationFebruary 21, 1933, Serial No. 657,786 a l -In Austria June 17,1932 I 1 jinvention relates to an electric timeiuse and has for its object toenhance the reliability of timing and ignition 01' such fusesunder'all;possible working conditions. To'attain this ob- .iect it has been foundin practice tosbe essentialto adopt a. combinationof measures whichcontribute jointly to the achievement of the aim in" The inventionisillustrated in the accompany- V ing=drawing which represents avertical section .oi an electric'time iuse according to the invention. f

' The ruse comprises a cartridge case I contain-f 5 ing amatch head 2and a retarding .charge 5. The match head is carried by electricleading-in wires 1 which enter the cartridge through a ing the matchhead. 1

. According to the invention the match head comprises a core of easilyignitable material which immediatelysurrounds the fuse wire, and anouter coating 3 capable of generating an intense heat. The coatingconsists of a metal powi5 der of iron, aluminium, zinc,.antimon y,zirconi um, or the like mixed with an oxygen carrier in the form of achlorate or nitrate, for instance potassium chlorate or barium nitrate.A mixture in about equal proportions of metal and oxygen 20 carrier hasbeen shown to give the best results. Several. metals can beusedtogether.

In order to concentrate the heat generated by the match head on theforward end of the retarding charge 5, the thick wall of the surrounding25 cylinder 4 istapered at the end which faces the match head, as shownin the drawing. By this arrangement the extreme end of the charge willbe surrounded by a ring of insulating air, and heat which wouldotherwise be dissipated through the cylinder I and through the cartridgecase, will be available for ensuring a reliable ignition of theretarding charge. v

For the. retarding charge a mixture of iron powder and an oxygencarrier, for instance potas- 5 sium permanganate, is employed. Since thepotassium permanganate has a strongly oxidizing influence on the ironwhich would be detrimental to prolongedstorage and since it also causesthe iron to burn too rapidly with considerable heat generation, isnecessary to add a neutral substance which will check oxidation andretard the combustion. For this purpose the iron powder is mixed with aphlegmatizing substance," for instance chalk, capable of enclosing andadhering to the iron particles. The iron powder is mixed with the chalkbefore the oxygen carrier is added. Treated in this manner the iron willbe protected from over-rapid oxidation, and 50 the charge will burnslowly anduniiormly, very little heating of the cartridge will'take,place, and

premature ignition of the explosive charge will be prevented. A suitablemixture is obtained case.

finely ground chalk, and 30 parts potassium permanganate Since the speedof the combustion is dependent on the gas pressure in the cartridge, itis essential to maintain the pressure free from fluctuations owing toleakage through the cartridge For'this purpose the closing plug 6, whichis made of lead or other compressible material, is hermetically sealedto the cartridge case by pressing circumferential and substantiallycontinuous grooves 8 into cartridge case and plug. 1 This compression ofthe plug is made so that a simultaneous hermetic sealing of the plug tothe leading-in wires 7, will be effected.

I claim:

1. An electric time fuse comprising in combination a fuse case open atone end and closed at the other end, lead-in wires, a plug of yieldingmaterial longitudinally traversed by the said lead-in wires and adaptedto form a closure of the open end of the saidrcase without any leakage,an electrically fired match head attached to the said wires and coatedexteriorly with a mixture of metal powder and an oxygen carrier, acharge of a retarding composition composed of iron particles coated witha neutral phlegmatizing substance and mixed with an oxygen carrier, ashell containing the said retarding composition closely fitting withinthe said fuse case and having its end nearest to the said match headtaperedly reduced in thickness of wall, and a priming charge locatedbetween the outer end of the said shell and the closed end of the fusecase, substantially the case.

3. In an electric time fuse as claimed in claim I the said retardingcomposition consisting of iron} particles coated with chalk and mixedwith po-j tassium permanganate. 7

4. In an electric time fuse as claimed in claim 1 20 the said retardingcomposition consisting of iron particles coated with chalk and mixedwith potassium permanganate, these ingredients being used in theproportions of 15:3:30 respectively.

KONRAD SCI-IAFFLER-GL6SSL.

AM] m

